The present invention relates generally to a fuel tank for use in motor vehicles, etc. and more particularly, to an oil filler portion thereof.
Some fuel tanks for motor vehicles include a valve mounted to a filler tube for fuel supply. This valve may be provided with a vent tube for ensuring vent operation upon fuel supply or an evaporation valve for conducting evaporated fuel within the fuel tank to a canister. Arranged within a valve main body is a shaft which has an end projecting into the filler tube. Upon fuel supply, by insertion of a nozzle of an oil gun into the filler tube, a shutter within the filler tube is opened, thereby pressing the shaft to open the valve main body. For further information, see, for example, JP-U 2-100922.
With such conventional fuel tanks, however, there arise the following problems:
Upon fuel supply, if a tank main body is supplied with a large amount of fuel, a pressure within the tank main body is increased. When this pressure exceeds a pressure for opening a check valve, the check valve is opened, and thus the evaporation tube is opened. With the evaporation tube opened, a fuel level which is rising upon fuel supply cannot be restrained by a level restraint valve, resulting in fuel oversupply exceeding a predetermined level. For solving this problem, a shutout valve can be provided to the evaporation tube in the vicinity of the check valve so as to be closed when detecting insertion of the nozzle of the oil gun. However, it is necessary to provide the shutout valve and an apparatus for detecting an inserted state of the nozzle of the oil gun, resulting in complicated constitution and increased manufacturing cost.
Further, with regard to a valve seal for the conventional fuel tanks, it is difficult to weld to the cylindrical filler tube a flat base plate on all periphery thereof, requiring a lot of working time. Moreover, due to sealing separately carried out in two portions between the filler tube and the base plate, and between the base plate and a bracket, possible leakage is increased, requiring high accuracy welding, etc. for improving a reliability, resulting in an increase in manufacturing cost.
Still further, if fuel supply is carried out with the shutter not fully opened due to a insufficient insertion amount of the nozzle of the oil gun, fuel is supplied with the vent cutout valve out of operation. Thus, vent operation by the vent cutout valve fails to be ensured, so that a level restraint fails to be carried out when the fuel tank is full, resulting in impossibility of ensuring an air chamber in the upper portion of the tank main body. Moreover, if fuel supply is carried out with the nozzle of the oil gun incompletely inserted, nonexecution of a level restraint causes a relief valve to open every fuel supply when the fuel tank is full, increasing a load applying to the tank main body.
It is, therefore, an object of the present invention to provide a fuel tank which allows correct fuel supply without any leakage and increase in manufacturing cost.